Air-oxygen mixing apparatus for hospitals



AIR-OXYGEN MIXING APPARATUS FOR HOSPITALS Filed Feb. 9. 1952 B. H. ACOMB Oct. 23, 1956 2 Shee ts-Sheet 1 WM w 1 INVENTQR BYRON H. ACOMB Oct. 23, I956 B. H. ACOMB I AIR-OXYGEN MIXING APPARATUS FOR HOSPITALS 2 Sheets-Sheet 2 Filed Feb. 9. 1952 2 o 8 6 ll DELIVERY OR BACK PRESSURE PSI B 6 W l c V m M H R M w 10 P W 4W 2I-L IR /\A 1N m I 7 M m Y X 0.

MOTIVE FLUID QS E a252- United States Patent AIR-OXYGEN MIXING APPARATUS FOR HOSPITALS Byron H. Acomb, Somerville, N. J., assignor to Union garlllide and Carbon Corporation, a corporation of New Application February 9, 1952, Serial No. 270,826 12 Claims. (Cl. 137-111) An air lock has found application in the delivery rooms of hospitals for initiating respiration in new born infants. At first oxygen under a few pounds pressure is supplied and the pressure released in cycles within the air lock until breathing begins. After breathing has started, a mixture of air and oxygen is supplied for a desired period. The air used has to be water-compressed and free of oil vapor; therefore, no air from the usual motor driven compressor is suitable. It has been the custom to keep the water-compressed air and oxygen in separate pressure cylinders, which has required regulators and valves for each cylinder in order to get the desired mixing. A nurse has to refer to a graph or appropriate table to indicate the quantities of each component necessary to obtain the desired mixture, since oxygen of course exists in the compressed air. I has been found that the suitable water-compressed air has been the more diflicult to keep on hand, perhaps because it is a special product not used in industry, and it has been difiicult to estimate the amount needed to be kept on hand based on somewhat indefinite future needs.

This invention relates to an apparatus for eliminating the danger of the supply of water-compressed air running out, and has for an object to do away with the need for such storage cylinders of compressed air. Another object is to simplify the required apparatus and render the mixing of oxygen and air in the desired proportions easier and simpler.

Specifically, this is accomplished by using an injector for forcing atmospheric air into the air lock under the impetus of a jet of oxygen under pressure. Unlike the usual injector, the injector in the present invention contains a pressure responsive device for enlarging the air passage to the mixture to increase the percentage of air in the mixture as [the flow and pressure of oxygen are reduced. A flowmeter on the oxygen supply line from a regulator is graduated to read in percentage of oxygen in the mixture supplied to the air lock and also may be graduated to read in liters of oxygen per minute. The medical profession has specified the need for oxygen being between 8 and 16 liters per minute and the total flow of oxygen plus air being substantially constant at 16 liters per minute. By a control valve on the oxygen supply line, the proportion of air to oxygen may be varied easily within the specified limits and the total gas flow of both air and oxygen is substantially a constant value.

Referring to the drawings:

Fig. 1 is a line view of the apparatus used.

Fig. 2 is a longitudinal section through the injector portion of the apparatus.

Fig. 3 is a detail of a modified embodiment whereby higher velocities of oxygen are obtained where higher back pressures in the mixture delivered are desired.

Fig. 4 is a graph showing the relation of quantity of air in liters per minute to the quantity of oxygen delivered in the same terms by the apparatus of Fig. 2 in the presence of a back pressure varying cyclically.

Fig. 5 is a more detailed chart showing the characterice istics of the present invention of Fig. 2 for different quantities for air and oxygen when different back or delivery pressures are desired.

Fig. 6 shows different characteristics obtainable for the relation between the quantity of induced fluid or air and the quantity of motive fluid or oxygen supplied by modifications of the injector.

Fig. 7 is a modified type of injector such as is capable of producing the graph 32 of Fig. 6.

Fig. 8 is another modified embodiment of the injector for the production of a graph according to that designated 31 in Fig. 6.

As shown briefly in Fig. 1, the apparatus comprises a two-stage fluid pressure regulator A delivering oxygen under approximately 100 pounds per square inch pressure through the flowmeter B past the control valve C and thence through the injector D for mixing atmospheric air with the oxygen and delivering the mixture to the air lock E. The combination of regulator flowmeter and control valve is similar to that disclosed in the prior applications of W. J. Jacobsson, Serial No. 54,902, filed October 16, 1948, for Fluid Pressure Regulator, now abandoned, and Serial No. 115,678, filed September 14, 1949, for Flowmeter, the latter being now Patent No. 2,655,041, dated October 13, 1953.

A cylinder of compressed oxygen delivers gas to the connection 10. The pressure gauge 11 indicates the pressure or degree of exhaustion in the oxygen supply cylinder of the gas delivered to the first or high pressure stage regulator 12 and thence to a second stage regulator 13.

The flowmeter is of the type having a ball within a vertical upwardly divergent and inner transparent tube 14 through which passes the gas the flow of which is to be measured. The flow rate is determined by measuring the upward displacement of the ball visible through the outer transparent tube illustrated. The movable valve element 15 is between the flowmeter and injector to control the quantity of oxygen being delivered to the injector. As shown in Fig. 2, the oxygen is delivered to the supply passage 16 for motive fluid to the injector. A tapered nozzle 17 contains a constriction .021" in diameter, formed in this case by a drill. The throat 13 in which nnxing of oxygen and atmospheric air occurs is tapered to the same angle as that of the nozzle 17. The mixture passage 19 is .067 inch in diameter formed by a #51 drill and leads through a connection 20 to the air lock E.

A passage 21 for the induced air is more than large enough to supply all the air that may be needed. The clearance or separation between the outer walls of the nozzle 17 and inner walls of the throat 18 constitutes a variable constricted passage that determines the quantity of air supplied to the mixture.

Unlike the usual injector, that of the present invention is provided with a pres-sure responsive device which automatically increases the quantity of air supplied to the mixture as the flow, i. e., pressure of oxygen is reduced. For this purpose, a passage 22 leads from the oxygen supply passage 16, so that oxygen pressure supplied to the injector acts upon a piston 23 supplied with an appropriate 0 ring 24 for sealing purposes. A spring 25 acts upon the piston 23 against the pressure of oxygen on top of the piston. For convenience in manufacture and adjustment, the throat 18 is formed in a removable and adjustable hollow stem 26, also provided with suitable 0 ring packing 27 to obtain the proper sealing. The separate end portion 28 functions as a lock nut to retain the hollow threaded stem 26 in its adjusted position.

To adjust the injector for use, the hollow stem 26 is lowered or backed off to give more than the desired clearance between the nozzle and throat. With the valve 15 slightly closed to obtain a flowmeter reading of 16 liters per minute or 100% oxygen, the pressure of the oxygen delivered to the injector is 90 pounds per square inch. The threaded stem 26 is then moved inwardly or upwardly until there-is no-movement of air through passage- 21. In this position, the throat 18 and. nozzle 17 are in contact and no air is induced. In this position, the lock nut 23 is tightened to retain the threaded stem in this position of adjustment. Further closing of the valve 15. reduces the flow and pressure of oxygen supplied to the injector, causing the piston to be moved upwardly under influence of the spring and causing t e constricted air passage between the walls of the nozzle 17 and the throat 13 to be enlarged. This. enlargement is in proportion to the reduction in pressure and flow of oxygen. In this embodiment spring 25 is one of constant rate, that is, one having its compression proportional to the pressure applied to it. Only a very small movement oi": .647 for the piston upwardly fromrits position of 100% oxygen and no air is suflicient when the flow of oxygen is reduced to 8 liters per minute to. cause the air intake to be also 8 liters per minute. Due to the atmospheric air containing oxygen, a flow of 8 liters of oxygen per minute is equivalent to 60% oxygen flow to the mixture. As illustrated in the drawing, the taper given the nozzle and throat is substantially in Fig. 3 is shown an embodiment whereby the injcctor may supply the desired mixture of oxygen and air under slightly higher back or delivery pressures than that for which the device of Fig. 2 is adapted, due to the constricted portion of the oxygen passage 16a having a slightly flaring mouth 29. As before, the throat 18a is formed in the hollow stem 26:: and the clearance between the walls of the nozzle 17a and throat 18a determines the quantity of air induced into the mixture.

Fig. 4 shows a substantially straight line graph 30 correlating the quantity of air induced with the average flow rate or quantity of oxygen as motive fluid supplied to the injector of. Fig. 2 in which back pressure is usually cyclically varied from about 1 to 3 pounds per square inch in the respiratory-air lock E. Since the sum of the air and oxygen supplied to theniixture is constant, this graph shows that, at 16 liters of oxygen per minute supplied to the injector,.the air. supplied is zero, or, in other words, the nozzle touches the walls of the throat. When 12 liters of oxygen per minuteare supplied to the injector by controlling the movable valve member 15, the air supplied is shown. to be 4 liters per minute.

Fig. 5 is a more detailed graph representing the characteristics obtained in flow through this injector. The ordinates of this chart are the liters per minute for induced air flow, while the delivery or back pressure in pounds per square inch is theabscissa. The lines sloping downwardly to the right are constant oxygen flow lines in liters per minute identified by the numerals arranged along the interruption to the horizontal line that would indicate 1 liter per minute of air. For example, following the slightly curved inclined constant oxygen flow line ending at the numeral 8, indicating 8 liters of oxygen per minute, and following this line to a value for 8 liters of air per minute, it will be seen that the back pressure for these values is approximately 2.3 pounds per square inch. It is also seen that through this intersection passes the somewhat upstanding curved line designated 1 to 1 ratio, which means that the ratio of oxygen to air is l to. 1 and, as previously stated, will provide a 60% oxygen concentration in the oxy-air mixture. The inclined line indicating 12 liters of oxygen per minute intersects the horizontal line for 4 liters of air per minute, which is a 3 to 1 ratio and indicates that a higher back pressure of 5 pounds per square inch could be possible, although such higher back pressure may never be used in the air lock. Since the flow of each component of the mixture is different throughout the pressure cycle in the air lock, the recorded: flows indicated by the. charts of Figs. 4 and 6 are average flows of. gases .to the air lock-..

4. Fig. 5 shows flow conditions at any given time within the cycle.

Fig. 6 shows two radially different types of discharge characteristics 31 and 32 for the injector which may be obtained by the modifications illustrated in Figs. 7 and 8.

The embodiment illustrated in Fig. 7 shows the type of injector capable of enabling a discharge characteristic such as that shownby the dot and dash line 32 to be possible. Analogous parts in Fig. 7 are designated by the same numerals used in Fig. 2,. except that the additional letter (b) has been added. The piston 23!) has the spring 25b cooperating with its upper side which in this case is opposite to the fluid pressure on the lower side. An additional piston 33 is provi ed as illustrated for cooperation withthe spring 34, pressing the piston 33 against the action of fluid pressure applied on the lower side of the piston and conveyed through the passage 35. The spring 34 is weaker than the spring 2511, so that, as the flow and pressure of the motive gas increases, the piston 33 is raised to reduce the intake opening for induced fluid between the throat 13b and the nozzle 17!).

As illustrated, stops are provided on each side of the piston 33, and, after the piston 33 reaches the upper end of its. travel, an increase in motive fluid pressure will compress the spring 25b more substantially, causing the. opening for induced fluid to increase by the nozzle 17b being raised; A vent 36 is provided so that air within the spring'chamber will not be trapped and compressed, thus restricting the upward travel of piston 23.") and also in case any motive fluid passes the sealing O ring 241) in the piston 23]). The piston 33 and also the stem 26]) are provided with suitable packing, and the same is true of the body of the nozzle 17.) back of its taper, as illustrated; By changing the relative strengths of the springs, the inclination of each portion of the characteristic line 32 may be changed.

In Fig. 8, the weaker spring 25c is placed above the piston 23c in order to obtain the characteristic shown by the graph 31' in Fig. 6. The stiffer spring 340 cooperates with the piston 33c. As the flow and pressure or" motive fluid increases, the piston 230 is first raised more than is the piston 33c, elevating the nozzle 17c and causing an increase in the flow of induced fluid. When the piston 23?: reaches its maximum height, limited by the stop illustrated, the piston 33c begins to raise more substantially against the stiffer spring 20, reducing the opening provided for induced fluid between the throat 18c and the outer surface of the nozzle 17c.

Among the advantages of this invention may be men tioned' that no longer is it necessary for the hospital delivery rooms to keep on hand water-compressed air, nor is a regulator needed for the air. The space occupied by the compressed air cylinder, regulator, valve and piping, has been eliminated. The flowmeter for the motive fluid supplied to the regulator is graduated in percentage of oxygen mixture being supplied to the air lock, so that a nurse finds it easier to obtain the desired proportion of air and oxygen mixture without having. to refer to a chart or table, it being only necessary to read the graduations on the flowmeter B. Since the medical specifications contemplated a constant quantity of fluid, namely 16 litersper minute, being supplied to the air lock, the present injector has been designed to provide mixtures from a l to l ratio of air and oxygen to a flow of oxygen. More specifically, the piston 23 in Fig. 2 moves a longitudinal distance of .047 of an inch from its positionforv 100% oxygen to its position for 8 liters per minute ofair and 8 liters per minute of oxygen or 60% oxygen. The only time the threaded stem 36 is adjusted is when starting the apparatus for test or calibration. The straight line characteristic 30 in Fig. 4' depends on the combination of the oxygen constriction in the nozzle, the supply of oxygen under. uniform pressure at a given setting,.the induced air constriction between the walls of the throat and nozzle, the area of the mixing passage 19, and the spring 25 having a constant rate. At present, the main use of this invention is with the air lock mentioned, although it is possible other uses for the injector discharge might be found in hospitals having an oxygen tent or mask. No other uses for the injector of this invention are known at present. The modifications illustrated in Figs. 7 and 8 have been disclosed, in event some other medical authority might desire diiterent operating characteristics.

What is claimed is:

1. In apparatus comprising an air lock of the type used in hospital delivery rooms for new born infants, a passage for supplying thereto oxygen under pressure, an oxygen regulator in said passage, a control valve also in said passage on the outlet from the regulator, and a flowmeter in said passage between said valve and regulator, the combination therewith of the improvement including an injector in said passage between said air lock and valve having passages for utilizing oxygen from said valve as the motive fluid and atmospheric air as the induced fluid, said injector containing an air passage and a throat into which said air is drawn for mixing the same with oxygen, and containing a device responsive to the pressure of oxygen from said valve for increasing the size of the air passage in said throat as the flow of oxygen to said injector is reduced.

2. Apparatus according to claim 1 in which said flowmeter is graduated in percent of oxygen in the oxygenair mixture supplied to said air lock.

3. Apparatus according to claim 2 in which the average mixture supplied bears a substantially straight line relation between the quantities of air and oxygen with 8 to 16 liters of oxygen flowing per minute and a total oxygen plus air flow of 16 liters per minute at all times.

4. Apparatus according to claim 1 in which a constriction in the oxygen supply passage is located in a nozzle directed into said throat and the air passage in said throat around said nozzle is reduced with respect to any other portion of the air passage in the injector.

5. An injector having a passageway for motive fluid, a passageway for induced fluid, a throat into which the induced fluid is drawn by the motive fluid, said throat comprising two portions at least one portion of said throat being axially movable toward and from the other portion to control the size of a portion of the passageway for induced fluid, a pressure responsive device connected to the passageway for motive fluid for moving said movable throat portion to increase the flow of induced fluid as the pressure and flow of motive fluid decreases.

6. An injector having a passageway for motive fluid, a passageway for induced fluid, a throat into which the induced fluid is drawn by the motive fluid, said throat comprising two portions axially movable toward and from the other, a pair of fluid pressure responsive devices, springs acting on each said device, one spring cooperating with one of said devices being lighter than the other, each of said throat portions being connected for movement by one of said pressure responsive devices, and a stop for limiting movement of that one of the pressure responsive devices having the lighter spring, each of said pressure responsive devices being connected with the motive fluid passageway, whereby the pressure responsive device having the lighter spring will adjust the quantity of induced fluid supplied to said throat until said pressure responsive device having the lighter spring reaches its stop after which said induced fluid supply will be varied in response to pressure of the motive fluid on the other device.

7. An injector having a casing, a passage therein for motive fluid, a passage for induced fluid, a throat in which mixing of the motive and induced fluids occurs,

a body in which said throat is formed, an outlet passage in said body for the fluid mixture, a nozzle at the termination of said motive fluid passage and shaped to extend into said throat whereby the clearance between said nozzle and throat determines the size of the passage for induced fluid just prior to mixing the fluids, at least one of said nozzle and body being yieldably mounted, a pressure responsive device movable under pressure of the motive fluid and carrying said movable one to vary said clearance, and a spring opposing movement of said device under pressure of motive fluid.

8. An injector having a casing, a passage therein for motive fluid, a passage for induced fluid, a throat in which mixing of the motive and induced fluids occurs, a body in which said throat is formed, an outlet passage in said body for the fluid mixture, a nozzle at the termination of said motive fluid passage and shaped to extend into said throat whereby the clearance between said nozzle and throat determines the size of the passage for induced fluid just prior to mixing the fluids, each of said body and nozzle being yieldably mounted, a pres sure responsive device carrying said nozzle, a spring cooperating with said casing and device for opposing movement of said nozzle under pressure of said motive fluid, another pressure responsive device movable under pressure of the motive fluid and carrying said body, and another spring cooperating with said casing and second mentioned device for opposing movement of said body.

9. An injector according to claim 8 in which one of said springs is stronger than the other.

10. An injector according to claim 9 in which each of said pressure responsive devices is provided with a stop to limit the extent of its travel in each direction.

11. Apparatus according to claim 1 in which the injector has a spring of constant rate cooperating with a piston movable under a change in oxygen pressure and flow between a flow of 8 liters of oxygen per minute and a flow of 16 liters of oxygen per minute, the oxygen supply passage in the injector containing a constriction having a diameter of .021 inch and the passage in which mixing of air and oxygen takes place having a diameter of .067 inch whereby the flow of oxygen plus air remains constant between flows of 8 to 16 liters of oxygen.

12. In an apparatus comprising a gas pressure lock in which the pressure is changed cyclically, a connection to said pressure lock through which a gas mixture is supplied, a mixing chamber in said connection, a supply pipe for one gas under pressure leading to said chamber, means for controlling the pressure of gas supplied to said chamber through said pipe, and a passage means for another gas leading to said chamber, the combination therewith of the improvement for insuring a substantially fixed average quantity of gas mixture being supplied to said pressure lock, said improvement including an injector in which said chamber is located and to which said supply pipe and passage means are connected, the gas through said supply pipe being the motive fluid and that through said passage means being the induced fluid, and a device in said injector responsive to pressure of said motive fluid for increasing the quantty of induced fluid supplied to said mixing chamber as the pressure and quantity of motive fluid is reduced.

References Cited in the file of this patent UNITED STATES PATENTS 1,075,408 Deckeback Oct. 14, 1913 1,421,843 Schmidt July 4, 1922 1,421,845 Schmidt July 4, 1922 1,592,305 Lewis July 13, 1926 1,933,733 Hess NOV. 7, 1933 2,162,242 Branower June 13, 1939 

